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1.
The reproduction of raptors strongly depends on food resources. It is unclear whether predators experience superabundant food during cyclic peaks of prey populations. In order to test this hypothesis, four pairs of Great Horned Owls Bubo virginianus with two young were subjected to brood size manipulations during high densities of cyclic Snowshoe Hare Lepus americanus populations in southwestern Yukon, Canada. Broods older than 35 days were temporarily enlarged by one, and then by two, young. No effects were observed when one owlet was added, but the addition of two young resulted in significant weight losses in manipulated broods. Females with enlarged broods moved farther from their nest sites at night, presumably reflecting increased hunting effort, and also spent less time near the nest during the day. Food additions to enlarged broods returned the parental behaviour to normal. We conclude that these large predators did not experience superabundant food at this stage of the breeding season during a peak in cyclic prey. 相似文献
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MARKUS WEITERE REAS VOHMANN NADINE SCHULZ CATHERINE LINN DÉSIRÉE DIETRICH HARTMUT ARNDT 《Global Change Biology》2009,15(12):2838-2851
Climate warming is discussed as a factor that can favour the success of invasive species. In the present study, we analysed potential fitness gains of moderate warming (3 °C above field temperature) on the invasive clam Corbicula fluminea during summer and winter. The experiments were conducted under seminatural conditions in a bypass-system of a large river (Rhine, Germany). We showed that warming in late summer results in a significant decrease in the clams' growth rates (body mass and shell length increase) and an increase in mortality rate. The addition of planktonic food dampens the negative effect of warming on the growth rates. This suggests that the reason for the negative growth effect of temperature increase in late summer is a negative energetic balance caused by an enhanced metabolic rate at limited food levels. Warming during early summer revealed contrasting effects with respect of body mass (no warming effect) and shell length (increased shell growth with warming). This differential control of both parameters further enhances the loss of the relative (size-specific) body mass with warming. In contrast, warming in winter had a consistently positive effect on the clams' growth rate as demonstrated in two independent experiments. Furthermore, the reproduction success (as measured by the average number of larvae per clam) during the main breeding period (April) was strongly enhanced by experimental warming during winter, i.e. by eight times during the relatively cold winter 2005/2006 and by 2.6 times during the relatively warm winter 2007/2008. This strong, positive effect of moderate winter warming on the clams' fitness is probably one reason for the recent invasion success of C. fluminea in the northern hemisphere. However, warm summer events might counteract the positive winter warming effect, which could balance out the fitness gains. 相似文献
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MARC DE HERT DAN COHEN JULIO BOBES MARCELO CETKOVICH‐BAKMAS STEFAN LEUCHT DAVID M. NDETEI JOHN W. NEWCOMER RICHARD UWAKWE ITSUO ASAI HANS‐JURGEN MÖLLER SHIV GAUTAM JOHAN DETRAUX CHRISTOPH U. CORRELL 《World psychiatry》2011,10(2):138-151
Physical disorders are, compared to the general population, more prevalent
in people with severe mental illness (SMI). Although this excess morbidity
and mortality is largely due to modifiable lifestyle risk factors, the screening
and assessment of physical health aspects remains poor, even in developed
countries. Moreover, specific patient, provider, treatment and system factors
act as barriers to the recognition and to the management of physical diseases
in people with SMI. Psychiatrists can play a pivotal role in the improvement
of the physical health of these patients by expanding their task from clinical
psychiatric care to the monitoring and treatment of crucial physical parameters.
At a system level, actions are not easy to realize, especially for developing
countries. However, at an individual level, even simple and very basic monitoring
and treatment actions, undertaken by the treating clinician, can already improve
the problem of suboptimal medical care in this population. Adhering to monitoring
and treatment guidelines will result in a substantial enhancement of physical
health outcomes. Furthermore, psychiatrists can help educate and motivate
people with SMI to address their suboptimal lifestyle, including smoking,
unhealthy diet and lack of exercise. The adoption of the recommendations presented
in this paper across health care systems throughout the world will contribute
to a significant improvement in the medical and related psychiatric health
outcomes of patients with SMI. 相似文献
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